1. Field of Invention
The invention relates to apparatuses for refacing a pipe connection and methods of refacing a pipe connection. The tools and methods described herein are particularly useful in the field of refacing drill pipe.
2. Description of Related Art
Tubular members, such as those used in oilfield applications, are often joined by threaded rotary shoulder connections. For example, rotary shoulder connections are used in the oil field to join sections of drill pipe and other related assemblies together. In a rotary shoulder connection, the shoulders, also referred to as faces and seals, are pressed together by the threads. The thread flanks jack against each other pushing the shoulders into each other. The shoulders provide strength and integrity to the connection and also work as seals to seal fluid pumped through the inside of the pipe. In a conventional rotary shoulder connection, each piece of pipe to be connected has one face/seal. If the condition of the face/seal is not smooth, it can leak and result in a connection failure. In addition, over-torque of the connection can over-stress the threads and shoulder and cause a connection failure. See API RP-7G-2/ISO 10407-2, Recommended Practice for Inspection and Classification of Used Drill Stem Elements, First Edition (August 2009).
High torque connections overcome many of the disadvantages associated with conventional rotary shoulder connections. High torque connections involve two seals, a primary seal and secondary seal. In a high torque connection, the primary seal makes contact at the same time as the secondary seal. The secondary seal serves as a torque-stop which prevents the connection from being over torqued and thereby avoids many of the disadvantages associated with conventional rotary shoulder connections.
Due to the primary and secondary seal design in high torque connections, it is critical that the length of the primary seal to the secondary seal remains the same. In establishing connections, both faces must be smooth and perpendicular to the thread direction to ensure a proper seal. If, however, a face is flawed or damaged with scratches, nicks, or other irregularities, it must be refaced prior to being used. During use of the pipe and assembly components, connections may be repeatedly made up and broken resulting in repeated face to face contact and wear. The resulting wear may result in sealing faces that are scored, nicked, or scratched or that no longer present a planar surface at right angles to the longitudinal axis of the pipe. When such conditions occur, the face-to-face contact may not form a proper pressure seal, thereby leading to connection failures. The connection must then be refaced prior to use.
Prior attempts to recondition the faces of pipe have employed methods that are costly or inconvenient and equipment that is expensive and/or unavailable in the field. For example, the faces may be re-tooled in a machine shop. However, re-tooling in a machine shop involves expensive and inconvenient transportation costs to transport the damaged/flawed pipe to the shop. There is a need for tools and/or methods for refacing high torque connections in the field.
U.S. Pat. No. 5,433,130 to Smith et al. describes portable shoulder dressing apparatuses. The shoulder dressing apparatuses include a mandrel, a mandrel securing means for securing the mandrel to the threaded end portion of the tubular connection; a piston assembly, the piston assembly being axially and rotatably movable relative to the mandrel; at least one cutter carried by said piston assembly; biasing means for applying a biasing force to the piston assembly to move the piston assembly axially relative the at least one shoulder and to urge the cutter into contact with the at least one shoulder, the biasing means being disposed between the mandrel and the piston assembly; and rotating means for rotating the piston assembly while the piston assembly is moved axially whereby the cutter can remove material from the at least one shoulder. In U.S. Pat. No. 5,433,130 the mandrel is attached to the connection via a threaded mandrel and the cutters are pressed into the shoulder to be refaced by a compression chamber employing pneumatic or hydraulic pressure.
U.S. Pat. No. 5,852,962 to Camille Fraering describes a field tool to reface high-torque pipe connections. The tool is known in the field as “The Lightning Refacer.” U.S. Pat. No. 5,852,962 sets forth difficulties associated with using a threaded mandrel and presents an alternative design. The Lightning Refacer instead incorporates, inter alia, a spring loaded cone that slides over the pin or box connection threads. The tool is held into position by the spring loaded cone, then a rotating body mounted with tungsten carbide cutters and powered by a portable driver, such as an 8″ angle grinder or Hole Hawg®, spins around the cone to reface the target surface.
The Lighting Refacer, however, has shortcomings when used in the field. For example, the tool operator must apply equal pressure, keeping faces at a right angel to the threads while pushing the refacing tool towards the connection faces. If unequal pressure is applied, the primary and secondary faces will be crooked with respect to the axis of the threads, and the length from one measurement to another measurement at 180 degrees away from the first will not be within acceptable tolerances. Maintaining equal pressure can be difficult for an operator resulting in crooked faces that are not within acceptable tolerances. In addition, even if equal pressure is applied, the refaced faces may still be crooked with respect to the axis of the threads if the tool is operated out of line with the axis of the threads. In addition, the tungsten carbide cutters can chip, causing irregularities on the face. Furthermore, for the Lighting Refacer to work, the physical condition of the threads must be smooth and free of any raised metal. Frequently, in high-torque connections used in drilling, the threads sharpen during repeatedly making up and breaking out the connection, resulting in threads that are raised and narrow. These sharpened threads impede the Lightning Refacer from easily sliding onto the threads. As such, often the threads must be dressed prior to refacing by using a dye grinder with a flapper wheel. This process is time consuming and can affect the subsequent accuracy of the reface.